[s-cars] Nasty Misses when Pushing the "93 S4

[Robert Myers]

Rich & Chris,

These symptoms also almost perfectly describe what happens with a single 
failing coil and this is what I'd consider the prime suspect.

Agreed - IF the MAP sensor is bad the VMAP is an excellent 
substitute/upgrade for the MAP sensor.  Note - that is, IMO, a pretty big 
"IF".  My wager would be that replacing the MAP (pressure transducer) with 
a VMAP will not solve your immediate problem.  However, replacing the 2.5 
bar PT with a VMAP is a possible good first step toward an upgrade.  Just 
don't be disappointed if it doesn't solve the immediate problem.

If you are looking toward an upgrade, Chris, a VMAP is almost essential for 
any significant boost upgrade.  The OEM 2.5 bar PT must be replaced with a 
PT capable of measuring MAP above 2.5 bar.  The Bosch 3.0 bar PT is NLA 
from Bosch.  I understand there are still some available from tuners who 
may have squirreled away a supply back when they were still available but 
these are now being used as only one component of an upgrade and are not 
sold separately.

The VMAP, by itself, will do virtually nothing toward supplying better 
performance but without it or an equivalent little is possible.  You will 
also need software in the form of two upgraded chips.  Such software is 
available from a number of sources.  It is not all the same software and 
there are differences in the behavior of engines controlled by different 
software.  Some possible choices are more or less equivalent.  Others 
behave differently - some doing quite well and some others with potential 
problems.

Significant performance gains are available with only a VMAP and 
appropriate software.  If you want to go safely beyond that level then 
hardware changes are also required.  These include items like a higher flow 
turbo, manifold changes, and higher flow injectors.  They also require 
considerably more expense.


At 02:17 AM 3/9/2005, Richard Tanimura wrote:

>Chris,
>
>Those symptoms sound familiar. Lots of us have BTDT. Could be a bad
>MAP sensor. Could also be a leak in the boost tract. Leaks are pretty
>common if you still have not changed your rubber hoses in a while.
>
>1. Pressure test the boost tract and listen for leaks. Check the
>clamps for tightness.
>
>2. If it isn't a leak and you are certain it is the MAP sensor I
>recommend VMAP. VMAP makes a dandy replacement to the Bosch 2,5 bar
>sensor.
>
>http://moreboost.com/
>
>Rich
>
>On Tue, 08 Mar 2005 20:47:03 -0800, Chris Holinger
><chris.holinger at gmail.com> wrote:
> > In Seattle, WA and was just diagnosed with a bad ECU pressure sensor.  The
> > Beast is shutting off the fuel when I really put the spurs to it so it¹s
> > bucking big time.  Or, as Bob Myers put it:
> > ³symptoms:  starts fine.  Idles fine. Cruises at constant speed 
> fine.  Will
> > accelerate if not done too enthusiastically.  If you get heavy on the loud
> > pedal you have a nasty miss.²
> > Suggestions based upon the fact that I would like to upgrade in the near
> > future?  Keep in mind, I just want to make it back to Chicago by the end of
> > the month safely.
> >
> > ŒPreciate any other help/advice you can offer.
> >
> > Thanks,
> > Chris
> > --
> > http://homepage.mac.com/cholinger/headinwest/
> >
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Bob
Http://Chips-Ur-S.com